Record year for salmon on Stanislaus

More salmon returned to the Stanislaus River this past fall than any other year since monitoring began a decade ago.

Alex Breitler

More salmon returned to the Stanislaus River this past fall than any other year since monitoring began a decade ago.

As of Wednesday, 7,019 fish had been counted passing a weir near Riverbank. Last year saw just 764 fish.

The increase is apparently part of a larger upward trend in the Central Valley as salmon continue to rebound from a dramatic decline caused in part by poor conditions in the ocean. That's where the migratory fish spend much of their lives.

But more fish is not always good news, said Doug Demko, whose consulting firm FISHBIO monitors salmon runs in San Joaquin Valley streams.

Many of these Stanislaus fish were bred in hatcheries, meaning they lack the genetic diversity of wild salmon and might be more susceptible to disease.

"It's human nature - we want a lot of fish; we think more is better," Demko said. "Personally, I'd rather see fewer fish in the river and have a higher percentage of natural fish."

What's more, Demko said the Stanislaus has quality habitat to support only about 3,000 spawning adult fish, so many of the baby fish produced by this year's 7,000-plus adults are unlikely to survive.

Finally, while 2012 was impressive compared with recent years, salmon populations were much higher historically before dams were built and water was diverted to farms and cities.

A look at how salmon fared in other major waterways as the fall migration comes to a close:

» Mokelumne River: 12,081 fish had passed Woodbridge Dam as of Christmas Day. That's a decline from last year's record of more than 18,500 fish but is still the fourth-highest yearly total dating back to 1940, according to data from the East Bay Municipal Utility District.

Last year, the federal government closed the Delta Cross Channel gate, ensuring that salmon stayed in the Mokelumne instead of wandering into the nearby Sacramento River.

The gate remained open this year, which might be part of the reason behind the decline from last year's record high, said Joe Miyamoto, the utility's manager of fisheries and wildlife.

This is the second consecutive year in which chinook salmon swam up the Calaveras through Stockton after a four-year absence.

In an email, however, Burr noted that the fish were unable to reach suitable habitat upstream of the Bellota weir. A long-overdue plan that officials have said will be released in early 2013 is supposed to improve fish passage at the weir.